A known door opening and closing system for vehicle is disclosed in Japanese Patent Laid-Open Publication No. H06-146688. The known door opening and closing system for vehicle disclosed in Japanese Patent Laid-Open Publication No. H06-146688 includes a latch mechanism for switching an openable state and a closed state relative to a vehicle body of a vehicle door (i.e., an unlatched condition and a latched condition relative to a vehicle body of a vehicle door), an actuator for operating the latch mechanism, a handle body provided at a panel member of the vehicle door, a switch provided at the handle body for operating the latch mechanism through the actuator, a lock-unlock switch for switching a state enable to operate the latch mechanism and a state unable to operate the latch mechanism (i.e., an unlocked state and a locked state) using the switch, a G sensor for detecting an inertia force loaded on the vehicle, and a control circuit for controlling an driving of the actuator based on a detected signal of at least one of the switch, the G sensor, and the lock-unlock switch.
With the known door opening and closing system for vehicle disclosed in Japanese Patent Laid-Open Publication No. H06-146688, the actuator, thus the latch mechanism is operated by an input signal of the switch for switching the unlatched state and the latched state of the vehicle door. The locked state and the unlocked state are switched by an input signal of the lock-unlock switch (i.e., the normal state). In case the vehicle door is under the locked state and the G sensor detects the inertia force to the vehicle due to the collision such as car clash, a control means switches the vehicle door to be the unlocked state irrespective of the operation of the lock-unlock switch. Then, the unlocked state is maintained (i.e., emergency state). The known door opening and closing system enables to open the vehicle door both from inside and outside of the vehicle at the vehicle collision and enables the evacuation of the operator and the passengers from the vehicle. That is, the door opening and closing system for the vehicle includes a function to switch the open and closed conditions of the vehicle door between under the normal state and the emergency state by the detection of the inertia force by the G sensor provided in the vehicle.
Notwithstanding, with the door opening and closing system for the vehicle disclosed in Japanese Patent Laid-Open Publication No. H06-146688, there may be drawbacks as follows. That is, the door open and closed conditions of the vehicle door may not be switched in case the inertia force loaded to the vehicle as a whole is less than a predetermined value when the object is directly collided with the vehicle door from the side and when only a portion adjacent the vehicle door portion contacts the object. Because the impact to the vehicle door influences the opening and closing function of the vehicle door, it is desirable that the door open and closed conditions for the vehicle are switched even by the impact only to the vehicle door. In this case, the detection sensitivity of the inertia force loaded to the vehicle as a whole (i.e. the detection sensitivity of the G sensor) may be increased for obviating the drawback. However, in that case, the door open and closed condition of the vehicle is frequently and unnecessarily switched, which gives the unpleasant feeling to the occupants.
A need thus exists for a door opening and closing system for a vehicle and a door handle device which securely performs the switching of an open and closed conditions of the vehicle door when receiving the impact at the vehicle door.